A method for preparing biomechanical pulp from kenaf by treating it with ternary deep eutectic solvent assisted by biological enzymes

Abstract

The invention discloses a method for preparing biomechanical pulp by treating kenaf with ternary low eutectic solvent-assisted bioenzyme, comprising the following steps: cutting kenaf stalks into small segments, mixing with low eutectic solvents, reacting at 100-150°C for 30-60min, cooling, and solid-liquid separation to obtain pretreated kenaf stalks; washing the pretreated kenaf stalks to neutrality, mixing with composite enzymes, and performing enzyme treatment at 40-60°C for 30-120min, performing pulping treatment on the kenaf stalks after enzyme treatment, washing and screening the slurry to obtain biomechanical pulp; the composite enzyme is a composite enzyme of xylanase and lipase, or a composite enzyme of cellulase and xylanase. Pretreatment with a low eutectic solvent can effectively improve the treatment efficiency of the bioenzyme.

Description

Technical Field

[0001] The invention belongs to the technical field of papermaking, and in particular relates to a method for preparing biomechanical pulp by treating kenaf with the aid of a ternary low eutectic solvent and a biological enzyme. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] my country's forest resources are relatively scarce and it is difficult to meet the needs of the pulp and paper industry. Non-wood raw materials occupy an important position in the pulp and paper industry. Compared with wood raw materials, non-wood raw materials have problems such as low paper strength and difficult black liquor treatment. Therefore, choosing suitable non-wood fiber raw materials to solve paper strength and environmental protection problems has become an important direction for non-wood pulping.

[0004] Kenaf is an annual herbaceous fiber crop with high cellulose content and low lignin content. It is a good pulping raw material and can improve the selectivity of raw materials for the pulp and paper industry. However, due to the characteristics of kenaf density gradually increasing from the base to the tip, different water absorption, and thin fiber cell wall, the traditional chemical pulping process has problems such as uneven cooking, high energy consumption, difficult recovery of black liquor, and low yield. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing biomechanical pulp by treating kenaf with a ternary low eutectic solvent assisted by a biological enzyme. The use of a low eutectic solvent for pretreatment can effectively improve the treatment efficiency of the biological enzyme.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing biomechanical pulp from kenaf by treating kenaf with a ternary deep eutectic solvent-assisted bio-enzyme, comprising the following steps:

[0008] Cut the kenaf stalk into small pieces, mix them with a low eutectic solvent, react at 100-150° C. for 30-60 minutes, cool them down, separate the solid and the liquid, and obtain the pretreated kenaf stalk;

[0009] The pretreated kenaf stalks are washed to neutrality, mixed with a composite enzyme, and subjected to enzymatic hydrolysis at 40-60° C. for 30-120 min, the enzyme-treated kenaf stalks are subjected to pulping, and the pulp is washed to obtain biomechanical pulp;

[0010] The complex enzyme is a complex enzyme of xylanase and lipase, or a complex enzyme of cellulase and xylanase.

[0011] Xylanase can degrade xylan in plant cell walls and break it down into smaller xylose molecules, exposing cellulose. Lipase can remove fat from the raw materials and improve fiber performance. Cellulase can promote fiber fibrillation and improve fiber papermaking performance.

[0012] The synergistic effect of xylanase and lipase can improve the dispersibility of pulp, which is beneficial to the dispersion of fibers and the improvement of paper quality. The action of cellulase and xylanase can reduce the energy consumption of pulping and the amount of chemicals used, and can improve the physical properties of paper.

[0013] Research has found that kenaf stalks have a loose structure and low lignin content, which is more conducive to biological pulping. Using biological enzymes for pulping, instead of high-temperature and high-alkali chemical reactions, can reduce the use of chemical raw materials, reduce water pollution, and reduce energy consumption, which is in line with the development direction of the papermaking industry.

[0014] Effective pretreatment can break the stable internal structure of lignocellulose, improve the accessibility of enzymes to raw materials, and improve pulp properties. The low eutectic solvent method is a green pretreatment method with the advantages of low volatility, non-flammability, and recyclability. Pretreatment of kenaf with low eutectic solvents can improve the swelling of fibers and enhance the accessibility of enzymes.

[0015] In some embodiments, the mass ratio of xylanase to lipase is 1-3:1-3.

[0016] In some embodiments, the mass ratio of cellulase to xylanase is 1-3:1-3.

[0017] Preferably, the solid-liquid ratio of the kenaf stalks to the complex enzyme solution is 1:4-6. The solid-liquid ratio refers to the mass ratio of the dry weight of the kenaf stalks to the complex enzyme solution.

[0018] Preferably, the total dosage of the complex enzyme is 20-50 U / g.

[0019] Further preferably, during the process of treating the kenaf stalks with the composite enzyme, the kenaf stalks are intermittently kneaded and stirred so that the composite enzyme is in full contact with the kenaf stalks to increase the reaction sites.

[0020] More preferably, when the kenaf stalks are treated with the composite enzyme, the kenaf stalks are placed in a sealed bag for treatment.

[0021] Preferably, when the kenaf stalks are treated with the composite enzyme, the pH value of the system is 5-9.

[0022] In some embodiments, the low eutectic solvent is a mixture of choline chloride, ethylene glycol and p-hydroxybenzenesulfonic acid monohydrate, and the low eutectic solvent can dissociate cellulose, hemicellulose and lignin by destroying the chemical bonds between the lignin-sugar water compound complex, so that one or two components are dissolved. The mass ratio of choline chloride, ethylene glycol and p-hydroxybenzenesulfonic acid monohydrate is 8-13:1-4:0.1-0.3.

[0023] In some embodiments, the method further comprises beating, deflaking and papermaking the obtained biomechanical pulp to obtain paper.

[0024] Preferably, the refining is carried out in two stages, and the refining gap is 0.1-0.5 mm.

[0025] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0026] The present invention uses kenaf as raw material, adopts a low eutectic solvent and biological enzyme treatment to prepare biomechanical pulp, thereby improving the physical properties of paper, such as tear index, tensile index and ring crush index, etc., to meet the requirements of producing paper-based materials. The low eutectic solvent can be recycled and the amount of chemicals used can be reduced, thereby realizing the green utilization of kenaf stalks. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0028] Figure 1 This is a flow chart of preparing biomechanical pulp from kenaf by ternary deep eutectic solvent-assisted bio-enzyme treatment according to an embodiment of the present invention;

[0029] Figure 2 The SEM images of kenaf stalks before and after treatment with a deep eutectic solvent and an enzyme according to an embodiment of the present invention are shown, wherein a is a SEM image of kenaf stalk fiber raw material, b is a SEM image of fiber obtained by treating kenaf stalks with a deep eutectic solvent, and c is a SEM image of fiber obtained by treating kenaf stalks with a biological enzyme;

[0030] Figure 3 Physical properties of paper after DES-assisted bio-enzyme pretreatment. DETAILED DESCRIPTION

[0031] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0032] The present invention will be further described below in conjunction with the embodiments.

[0033] Example 1

[0034] 1. Heat and stir choline chloride, ethylene glycol and p-hydroxybenzenesulfonic acid monohydrate at 80°C in a certain mass ratio to form a clear and transparent liquid to obtain a low eutectic solvent;

[0035] 2. Peel the kenaf and cut it into small pieces of 2-3 cm, and mix it with the low eutectic solvent obtained in step 1 at a mass ratio of 1:10, react at 120° C. for 40 minutes, then dilute it with warm water, wash it to neutrality, and then dehydrate it;

[0036] 3. Put the kenaf raw material obtained in step 2 into a sealed bag, and add compound enzyme for bio-enzyme pretreatment. The total dosage of the two enzymes (xylanase and lipase) is 30 U / g, the compounding ratio is 2:1, the liquid ratio is 1:6, the temperature of bio-enzyme pretreatment is 50°C, the pH value is 5.5, and the treatment time is 60 min;

[0037] 4. Performing two-stage high-concentration refining on the kenaf obtained in step 3, wherein the first refining gap is 0.5 mm and the second refining gap is 0.2 mm, to obtain kenaf biomechanical pulp;

[0038] 5. The kenaf biomechanical pulp obtained in step 4 is subjected to high-concentration washing, and is screened through a pulp screen to obtain a fine pulp;

[0039] 6. The pulp obtained in step 5 is beaten with a PFI pulping machine at a beating degree of 40±2°SR, and then made into paper after debonding. The ring crush index of the paper is 10.26N·m / g, and the tear index is 1.47mN·m 2 / g, and the tensile index is 29.80N·m / g.

[0040] Example 2

[0041] 1. Heat and stir choline chloride, ethylene glycol and p-hydroxybenzenesulfonic acid monohydrate at 80°C in a certain mass ratio to form a clear and transparent liquid to obtain a low eutectic solvent.

[0042] 2. Peel the kenaf and cut it into small pieces of 2-3 cm, and mix it with the low eutectic solvent obtained in step 1 at a mass ratio of 1:10, react at 120° C. for 1 hour, then dilute it with warm water, wash it to neutrality, and then dehydrate it.

[0043] 3. Put the kenaf raw material from step 2 into a sealed bag and add a composite enzyme for biological enzyme pretreatment. The total dosage of the two enzymes (cellulase and xylanase) is 40 U / g, the compounding ratio is 1:3, the liquid ratio is 1:6, the temperature of the biological enzyme pretreatment is 55°C, the pH value is 5.5, and the treatment time is 60 min.

[0044] 4. The kenaf obtained in step 3 is subjected to two-stage high-concentration refining, wherein the gap of the first stage refining is 0.5 mm, and the gap of the second stage refining is 0.2 mm, to obtain kenaf biomechanical rough pulp.

[0045] 5. The kenaf biomechanical pulp obtained in step 4 is subjected to high-concentration washing, and is screened through a pulp screen to obtain fine pulp, and the yield is calculated.

[0046] 6. The pulp obtained in step 5 is beaten with a PFI pulping machine at a beating degree of 40±2°SR, and then made into paper after debonding. The ring crush index of the paper is 11.47N·m / g, and the tear index is 1.33mN·m 2 / g, and the tensile index is 34.01N·m / g.

[0047] Comparative Example 1

[0048] This comparative example is basically the same as Example 1, except that in step 2, no low eutectic solvent is added to treat the kenaf raw material, and only deionized water is added to make the mass ratio of kenaf 1:10, and paper cannot be made.

[0049] Comparative Example 2

[0050] This comparative example is basically the same as Example 2, except that in step 2, no low eutectic solvent is added to treat the kenaf raw material, and only deionized water is added to make the mass ratio still 1:10, and paper cannot be made.

[0051] Comparative Example 3

[0052] This comparative example is basically the same as Examples 1 and 2, except that: in step 3 of the control group, no composite enzyme is added to treat the kenaf raw material, and only deionized water is added to make the liquid ratio 1:6.

[0053] Table 1 Comparison of physical properties of biomechanical pulp prepared in Examples and Comparative Examples

[0054]

[0055]

[0056] Note: Comparative Examples 1 and 2 cannot be slurried, so there is no performance index test value.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing biomechanical pulp from kenaf by treating it with a ternary deep eutectic solvent assisted by a bio-enzyme, characterized in that: The steps include: Cut the kenaf stalks into small pieces, mix them with a low eutectic solvent, react at 100-150° C. for 30-60 minutes, cool them down, separate the solid and the liquid, and obtain the pretreated kenaf stalks; The pretreated kenaf stalks are washed to neutrality, mixed with a composite enzyme, and subjected to enzyme treatment at 40-60° C. for 30-120 min, the enzyme-treated kenaf stalks are subjected to pulping treatment, and the pulp is washed and sieved to obtain biomechanical pulp; The complex enzyme is a complex enzyme of xylanase and lipase, or a complex enzyme of cellulase and xylanase; The total dosage of the complex enzyme is 20-50U / g; When the kenaf stalks were treated with compound enzymes, the pH value of the system was 5-9; The low eutectic solvent is a mixture of choline chloride, ethylene glycol and p-hydroxybenzenesulfonic acid monohydrate, and the mass ratio of choline chloride, ethylene glycol and p-hydroxybenzenesulfonic acid monohydrate is 8-13:1-4:0.1-0.

3.

2. The method for preparing biomechanical pulp from kenaf by treating kenaf with ternary deep eutectic solvent assisted by bio-enzyme according to claim 1, characterized in that: The mass ratio of xylanase to lipase is 1-3:1-3.

3. The method for preparing biomechanical pulp from kenaf by treating kenaf with ternary deep eutectic solvent assisted by bio-enzyme according to claim 1, characterized in that: The mass ratio of cellulase to xylanase is 1-3:1-3.

4. The method for preparing biomechanical pulp from kenaf by treating kenaf with ternary deep eutectic solvent assisted by bio-enzyme according to claim 2 or 3, characterized in that: The liquid ratio of the complex enzyme is 1:4-6.

5. The method for preparing biomechanical pulp from kenaf by treating kenaf with ternary deep eutectic solvent assisted by bio-enzyme according to claim 1, characterized in that: In the process of treating the kenaf stalks with the composite enzyme, the kenaf stalks are intermittently rubbed and stirred.

6. The method for preparing biomechanical pulp from kenaf by treating kenaf with ternary deep eutectic solvent assisted by bio-enzyme according to claim 1, characterized in that: The method for making paper comprises the following steps: pulping the kenaf stalks after enzymatic hydrolysis, washing the pulp to obtain biomechanical pulp, beating, debonding and papermaking the obtained biomechanical pulp to obtain paper.

7. The method for preparing biomechanical pulp from kenaf by treating it with a ternary deep eutectic solvent assisted by bio-enzyme according to claim 6, characterized in that: The refining is carried out in two stages, and the refining gap is 0.1-0.5 mm.

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